A number of technical solutions have been proposed to allow liquids to be road transported in reusable containers. When the containers are not disposable, there is the need to return them to the sender to be reused several times.
Containers known with the acronym bag-in-drum are provided with an outer and substantially rigid shell inside which a bag is positioned and made of a polymeric film, for example polyethylene, polypropylene or polyurethane. The bag is intended for being filled by the sender with the liquid to be carried; once it reaches the destination, the bag is emptied and squashed. In order to aid the emptying of the bag and to avoid liquid remains in its inside, the addressee flows pressurized air in the outer shell to squash the bag and thereby achieve the complete ejection of the fluid initially contained.
EP 1501750 and EP 2476634 describe solutions of this type.
Containers have been proposed which are also collapsible in addition to have the inner bag. This feature allows minimizing bulks of empty containers, therefore being handier to manipulate and return to sender.
U.S. Pat. Nos. 5,366,090, 6,431,435, US 2012/0273485 and WO 2011/159979 describe this type of containers.
The Applicant found a drawback in solutions of the prior art, just concerning the possibility of collapsing the used containers and filling them again.
More in detail, outer shells of containers are rigid and box-shaped, as in examples described in U.S. Pat. No. 6,431,435, in US 2012/0273485 or in WO 2011/159979, or else they are reticular, i.e. defined by nets in metal meshes, as in the example described in U.S. Pat. No. 5,366,090.
In case of box-shaped shells, the walls are substantially rigid and not flexible since they have structural function: they must sustain the full container. When the inner bag has been emptied, an operator must manually pull down the shell walls, one on another. Vice versa, before filling again the inner bag, an operator must erect the shell by manually raising the respective parts, and in case constrain them one another by ropes or mechanical fastening.
On the contrary, the reticular shells have no structural function, but they are useful only for confining the inner bag inside a predefined volume, so that it can not do a belly-flop or overturn, the fluid pressure in the inner bag holding upright the container. An operator has to check if the metal rings defining the net meshes move correctly during the filling and the emptying of the inner bag. For example, horizontal rings must slide vertically, without jamming, on vertical metal rods defining the posts, towards the base or upwards, depending whether the shell has to be collapsed or erected. Among other things, when the container is erected, the operator must manually move the metal rings to their position next to the apposite recesses obtained on the posts.
Therefore, the active intervention of an operator is in any case necessary and this entails risks for his safety and delays in filling and emptying each batch of containers to be moved.